feather/css, a user-controllable theme & its utility classes

[will-hanlen]

see: https://nyc3.digitaloceanspaces.com/drain/hawk/demos/2024.5.10..13.51.45-feather2.html

changes:

• rewrites sky and hawk as (mostly) server rendered
• adds the feather css library (and its lengthy documentation... whoops)
  • ~1000 of the added lines are feather's documentation
• shrub for configuring feather's varaibles
• JS interface for keyboard navigating all clickable interfaces

[will-hanlen]

turning back into a draft, still has some small bugs with moving hawks around